40 CFR 312.28: Specialized knowledge or experience on the part of the defendant.

(a) Persons to whom this part is applicable per § 312.1(b) must take into account, their specialized knowledge of the subject property, the area surrounding the subject property, the conditions of adjoining properties, and any other experience relevant to the inquiry, for the purpose of identifying conditions indicative of releases or threatened releases at the subject property, as defined in § 312.1(c).

(b) All appropriate inquiries, as outlined in § 312.20, are not complete unless the results of the inquiries take into account the relevant and applicable specialized knowledge and experience of the persons responsible for undertaking the inquiry (as described in § 312.1(b)).